This invention relates to heat conducting mechanisms; and more particularly, it relates to structures for such mechanisms which are suitable for conducting heat away from integrated circuit packages.
By an integrated circuit package is herein meant an enclosure which--a) contains one or more integrated circuit chips, b) has input terminals for receiving power and electrical signals, and c) has output terminals on which output signals are generated. Typically, the enclosure is made of ceramic, or plastic, or metal or an epoxy glass. These integrated circuit chips dissipate heat while the chips are operating; and thus the problem arises of how to prevent the temperature of the integrated circuit package from exceeding a certain limit above which the chips will malfunction.
To address this overheating problem, many prior art mechanisms for conducting heat away from the integrated circuit packages have been disclosed. See, for example, U.S. Pat. No. 4,791,983 by Nicol, et al. entitled "Self Aligned Liquid Cooling Assembly"; and see U.S. Pat. No. 5,323,294 by Layton, et al. entitled "Liquid Metal Heat Conducting Member and Integrated Circuit Package Incorporating Same."
Each mechanism which conducts heat away from an integrated circuit package does so by providing a thermal conduction path from the integrated circuit package to a coolant, which may be air or a liquid; and this thermal conduction path inherently includes a joint between the heat conducting mechanism and the integrated circuit package. If this joint is soldered, then the task of replacing a defective integrated circuit package becomes difficult. This problem is overcome if the joint is simply pressed together; however, a joint which is pressed together has a higher thermal resistance than a joint which is soldered together and thus the operating temperature of the integrated circuit package will be increased.
Now, the above-cited U.S. Pat. No. 5,323,294 addresses the problem of how to lower the thermal resistance between two components which are pressed together, by placing between those components, a compliant body which has microscopic voids therethrough and in which a liquid metal alloy is absorbed. Examples of this structure are shown in FIGS. 2, 5, and 6 of patent '294. Due to the presence of the liquid metal alloy, the thermal resistance between the two components is substantially reduced in comparison to the thermal resistance which would otherwise occur if those two components were simply pressed against each other.
However, the present inventors have discovered that certain drawbacks still exist even with the low thermal resistance which is provided in patent '294 by the structures of FIGS. 2, 5, and 6. By eliminating these drawbacks, which are described in the "Detailed Description" in conjunction with TABLE I and FIGS. 2A-2C, the thermal resistance of a pressed joint between two components is reduced to less than half the thermal resistance which is obtained by patent '294.